# Repository Guidelines

## Project Structure & Module Organization

This repository contains a small ESP8266/ESP32 Arduino project for monitoring water level with conductive electrodes and a small PHP endpoint for logging measurements.

- `arduino/arduino.ino` contains the Arduino sketch and main application logic.
- `server/log.php` accepts measurement POST requests and appends them as JSON Lines.
- `server/data-checker.php` is intended for hourly CRON runs and checks whether recent measurements are still being written.
- `server/functions.inc.php` contains shared PHP helpers, including JSON responses, HTTP requests, and Telegram notifications.
- `data/YYYY.jsonl` is created at runtime for logged measurements and should not be treated as source code.
- `README.md` gives the high-level project purpose.
- `LICENSE` contains licensing information.
- `.agents/` is reserved for agent/tooling metadata and should not be treated as firmware source.

Keep Arduino source files inside the `arduino/` sketch directory so Arduino IDE can open and build the project correctly.

## Build, Test, and Development Commands

Use Arduino IDE or `arduino-cli` with the ESP8266 or ESP32 board package installed.

Examples:

```sh
arduino-cli compile --fqbn esp8266:esp8266:nodemcuv2 arduino
arduino-cli upload -p COM3 --fqbn esp8266:esp8266:nodemcuv2 arduino
arduino-cli monitor -p COM3 -c baudrate=115200

arduino-cli compile --fqbn esp32:esp32:esp32 arduino
arduino-cli upload -p COM3 --fqbn esp32:esp32:esp32 arduino
arduino-cli monitor -p COM3 -c baudrate=115200

php -l server/log.php
php -l server/data-checker.php
php -l server/functions.inc.php
```

- `compile` verifies the sketch builds for the selected board.
- `upload` flashes the firmware to the connected board.
- `monitor` opens the serial console used by debug output.
- `php -l` checks the PHP scripts for syntax errors.

Adjust `--fqbn` and `COM3` for the actual board and port.

## Coding Style & Naming Conventions

Write C++ compatible with Arduino IDE and the ESP8266/ESP32 cores. Use two-space indentation, braces on the same line, and descriptive names.

- Constants: uppercase or clearly prefixed names, for example `PIN_LEVEL1`, `SLEEP_TIME_SEC`.
- Structs and types: PascalCase, for example `WaterLevels`.
- Functions: lower camelCase, for example `readLevels()` and `connectWifi()`.

Prefer small functions with one responsibility. Keep hardware pins, URLs, timings, and debug flags as constants near the top of the sketch.

For PHP scripts, keep them framework-free unless the project grows. Return JSON responses, use explicit HTTP status codes, and keep generated log files under `data/`.

Keep shared PHP helpers in `server/functions.inc.php`. Use the existing `telegram()` helper for Telegram notifications, and wrap notification calls so delivery failures do not change the HTTP response or stop measurement logging.

## Hardware Notes

For ESP8266 conductive level sensing, use external pull-down resistors from each `PIN_LEVEL1..4` input to `GND`. The common electrode is driven to positive voltage only during measurement.

Avoid ESP8266 boot/strap pins for level inputs when possible, especially `GPIO0`, `GPIO2`, and `GPIO15`. Also avoid `GPIO1`/`GPIO3` unless intentionally sharing the serial port. Prefer ordinary GPIO pins such as `GPIO5`, `GPIO4`, `GPIO14`, `GPIO12`, or `GPIO13`, depending on the board and wiring.

## Testing Guidelines

There is no automated test framework in this repository. Validate changes by compiling the sketch and testing on hardware.

Before committing firmware changes:

- Compile for the target ESP8266 or ESP32 board.
- Test `DEBUG == 1` for local level readings without Wi-Fi.
- Test `DEBUG == 2` for repeated Wi-Fi POST requests.
- Test `DEBUG == 0` for production sleep/wake behavior.

Before committing server changes:

- Run `php -l server/log.php`.
- Run `php -l server/data-checker.php` when the CRON checker changes.
- Run `php -l server/functions.inc.php` when shared helpers change.
- Test that non-POST requests return HTTP 405 with `Allow: POST`.
- Test a form POST such as `level1=1&level2=0&level3=0&level4=1`.
- Verify that a single compact JSON object is appended to `data/YYYY.jsonl`.
- Verify the CRON checker stays silent when `data/YYYY.jsonl` is missing, empty, younger than 45 minutes, or older than 3 hours and 45 minutes.
- Verify the CRON checker walks backward to the nearest valid JSON line when the last line is invalid.
- For notification changes, verify that Telegram messages are sent only when `level1..level4` differ from the previous saved measurement.
- Verify invalid level combinations such as `0100`, `1010`, and `1101` produce the measurement error notification without causing an HTTP error.

## Commit & Pull Request Guidelines

Current Git history is minimal and uses a simple message such as `Initial commit`. Keep future commits short, imperative, and specific, for example `Add WiFi timeout handling`.

Pull requests should include:

- A brief description of firmware behavior changed.
- Board model and Arduino ESP8266/ESP32 core version used for testing.
- Serial output or screenshots when debugging behavior changes.
- Any required configuration changes, especially Wi-Fi, server URL, or pin mapping.

## Security & Configuration Tips

Avoid committing real Wi-Fi passwords or private server endpoints when possible. For shared changes, replace secrets with placeholders and document required local values.